Keyframes - direct, shorter shortcut?
If you want to assign a key that always inserts the LocRotScale key at the current time, you have to do the following:


Go in the Blender Preferences, under Keymap and search for "Insert Keyframe".
There will be an entry under Outliner, unfold the "Insert Keyframe" by clicking on the small triangle in front of the checkbox.

You need to copy the "anim.keyframe_insert" for your own new "one button function"
Clear the search and open/unfold the User Interface keymappings.
At the bottom of the list you will find a button "+ Add New", click that and it should look like this, a new keymap line with "none" set in it

Where there is "none" you paste the "anim.keyframe_insert", and once you confirm it, the keymap changes to this:

There is a darkened "Keying Set:" and a "Confirm Successful Insert" that needs some attention. Select the "LocRotScale" in the dropdown-menu of the "Keying Set" and unhook the "Confirm Successful Insert" option, it should now look like this:

Now there is only one thing left, assigning a key (hopefully not used yet) to have the functionality per "one button".
For that just click on the big button right beside the "anim.keyframe_insert" textfield and then press a key. You can afterwards add some modifiers like "Alt", "Ctrl" .. etc.
When done, you can test it without having to close the Blender Preferences to adjust it or find a better key.


Happy Blending